There is a salaat of esteghsa from Hazrat Zehra SA for marriage which our teacher recommend. You can find in shiatoolkit as well
He should try his best with determination not to commit this sin and if he should seek Allah’s forgiveness.
He could also make a nazr that every time he commits this sin that he would fast one day for example. This may deter him.
I do understand that youth is a student and in demanding programme but he has to realise that it is wrong it is sin and if he can manage to time to disobey the Allah and then why he can organise some time for character building .
Marriage is the solution please help him in this important act which will protect him from haram.
Try to change friend curved daily life style